Modifications of cysteine residues in the transmembrane and cytoplasmic domains of a recombinant hemagglutinin protein prevent cross-linked multimer formation and potency loss.

BACKGROUND: Recombinant hemagglutinin (rHA) is the active component in Flublok®; a trivalent influenza vaccine produced using the baculovirus expression vector system (BEVS). HA is a membrane bound homotrimer in the influenza virus envelope, and the purified rHA protein assembles into higher order rosette structures in the final formulation of the vaccine. During purification and storage of the rHA, disulfide mediated cross-linking of the trimers within the rosette occurs and results in reduced potency. Potency is measured by the Single Radial Immuno-diffusion (SRID) assay to determine the amount of HA that has the correct antigenic form. RESULTS: The five cysteine residues in the transmembrane (TM) and cytoplasmic (CT) domains of the rHA protein from the H3 A/Perth/16/2009 human influenza strain have been substituted to alanine and/or serine residues to produce three different site directed variants (SDVs). These SDVs have been evaluated to determine the impact of the TM and CT cysteines on potency, cross-linking, and the biochemical and biophysical properties of the rHA. Modification of these cysteine residues prevents disulfide bond cross-linking in the TM and CT, and the resulting rHA maintains potency for at least 12 months at 25 °C. The strategy of substituting TM and CT cysteines to prevent potency loss has been successfully applied to another H3 rHA protein (from the A/Texas/50/2012 influenza strain) further demonstrating the utility of the approach. CONCLUSION: rHA potency can be maintained by preventing non-specific disulfide bonding and cross-linked multimer formation. Substitution of carboxy terminal cysteines is an alternative to using reducing agents, and permits room temperature storage of the vaccine.

Epidermal growth factor receptor regulates pancreatic fibrosis.

The development of pancreatic fibrosis has been shown to be a major component in several diseases of the pancreas including pancreatic cancer, chronic pancreatitis, and type 2 diabetes mellitus, but its actual role in the progression of these disorders is still unknown. This fibrosis is characterized by stromal expansion and the excessive deposition of extracellular matrix (ECM) that replaces pancreatic tissue. This eventually leads to dysregulation of ECM turnover, production of cytokines, restriction of blood flow, and often exocrine and endocrine insufficiencies. Activated pancreatic stellate cells (PSCs) have been identified as key mediators in the progression of pancreatic fibrosis, serving as the predominant source of excess ECM proteins. Previously, we found that overexpression of the growth factor heparin-binding epidermal growth factor-like growth factor (HB-EGF) in pancreatic islets led to intraislet fibrosis. HB-EGF binds to and activates two receptors, epidermal growth factor receptor (EGFR) and ErbB4, as well as heparin moieties and CD9/DRAP27. To understand the mechanism underlying the induction of fibrogenesis by HB-EGF, we utilized a hypomorphic allele of Egfr, the Waved-2 allele, to demonstrate that EGFR signaling regulates fibrogenesis in vivo. Using an in vitro cell migration assay, we show that HB-EGF regulates both chemoattraction and stimulation of proliferation of PSCs via EGFR activation.

Establishment of conditionally immortalized epithelial cell lines from the intestinal tissue of adult normal and transgenic mice.

It has proved to be impossible to culture epithelial cells from the gastrointestinal tract of adult animals. Researchers have had to use either cell lines derived from newborn rat small intestine or colon carcinoma cell lines that have retained some of the properties of the gastrointestinal mucosa. We have described a method for establishing conditionally immortalized cell lines from the stomach, small intestine, colon, pancreas, and liver from tissue obtained from a transgenic mouse strain carrying a temperature-sensitive mutant of the SV40 large T gene (the "Immortomouse"). This immortalizing gene has proved to be useful for establishing cell lines from a number of transgenic mice following crossbreeding of the Immortomouse with the transgenic mouse of interest. These cell lines are being used in numerous studies. In this review we describe the methods for developing such lines and list the range of cell lines that have been developed from colon, small intestine, stomach, liver, and pancreas of a number of transgenic mice.

Conditionally immortalized colonic epithelial cell line from a Ptk6 null mouse that polarizes and differentiates in vitro.

BACKGROUND AND AIMS: PTK6 is an intracellular src-related tyrosine kinase that regulates differentiation in the intestine, where knockout animals have increased proliferative activity and growth characteristics. To explore the phenotype further we attempted to establish epithelial cell lines from the intestinal mucosa. METHOD: We mated Ptk6 null mice with a tsSV40 large T transgenic mouse (Immortomouse) to obtain null mice carrying the SV40 gene. Intestinal tissues from these mice were cultured. RESULTS: We established a Ptk6 null epithelial cell line from the colonic mucosa. Consistent with a role of Ptk6 in cell differentiation, these cells have the characteristics of a stable progenitor cell. In monolayer culture, the cells form domes in the monolayer when confluent. When cultured on Transwell filters, the cells polarize and form an electrically resistant barrier. Formation of tight junctions was confirmed by demonstrating expression of ZO1 and occludin at the apical junctions, whereas E-cadherin localized to the basolateral membrane. When cultured in collagen gel, the Ptk6 null cells form complex organoids, some of which resemble cups of cells. These organoids contain cells with differentiated phenotypes. Using immunohistochemistry and confocal microscopy we have been able to identify villin-positive (absorptive cells) and a small percentage of mucin-containing cells (goblet cells) and chromogranin A-positive cells (endocrine cells). CONCLUSION: This conditionally immortalized cell line represents an excellent cell culture model system for exploring the mechanisms of cell function and epithelial differentiation in the colonic mucosa.